Movements of Arctic and northwest Atlantic Greenland sharks (Somniosus microcephalus) monitored with archival satellite pop-up tags suggest long-range migrations

Abstract

Greenland sharks (Somniosus microcephalus) are large carnivorous sharks that appear to be widely distributed in Arctic seas and in deep, cold temperate waters. In order to examine their movement patterns, diving behaviour and temperature preferences, pop-up archival transmitting tags (PATs) were deployed on 15 Greenland sharks up to 5.1m in length, both in the Canadian Arctic and in the northwest Atlantic off the eastern coast of Canada. Tags remained on the sharks up to 11 months (mean of 149 days, including four tags which came off prematurely) before popping off. All sharks travelled a minimum of 315km, and some as much as 1615km, at depths of up to 1816m. All tagged Greenland sharks in the Arctic exited the relatively shallow, coastal waters of Cumberland Sound before sexual maturation, presumably moving to spend their adult lives in the deeper waters of the Davis Strait to the north. All the presumably mature Greenland sharks tagged in the NW Atlantic moved up to 1000km off the continental shelf over abyssal waters to the south. There was extensive evidence of pelagic swimming in both regions, but diel vertical excursions into the water column were not observed. The mean temperature of 2.7°C recorded in the Arctic sharks was much less than the 7.9°C mean temperature observed in the Atlantic sharks, where a maximum temperature of 17.2°C was recorded. Our results indicate that Greenland sharks can inhabit very deep waters, and they can inhabit very cold waters, but they do not necessarily have to inhabit deep, cold waters. It is possible that Greenland sharks migrate offshore over very deep waters to mate and/or give birth.